The present invention relates to a method of manufacturing vacuum envelopes or vacuum envelope parts made of glass for electronic valves, particularly for cathode ray tubes, in which a substantially flat plate of glass is heated beyond the softening point and is deformed by means of an appropriately moulded stamp.
It is known to produce bulbs for electronic valves by means of glass blowing and appropriate further processing of the moulded glass body. Larger valves, particularly cathode ray tubes, such as image tubes and oscillograph tubes are normally manufactured so that the vacuum casing is composed of several individual moulded glass parts. A typical cathode ray tube bulb comprises a so-called valve neck, a so-called valve cone which is also the funnel-shaped part of the valve, and a front plate on the inner surface of which is arranged a fluorescent screen. In the same way, it is known to use a front dish which has a rim on its periphery instead of a plane-parallel front plate. The facing annular surfaces of the individual parts, which must of course be largely the same at their periphery, are then fused together or are connected together in vacuum-tight manner with the aid of a soldering material, e.g. a glass solder. Then, at a later point in time, the so-called valve stem is inserted in vacuum-tight manner into the free opening of the valve neck, the electron-producing system being mounted generally on the valve stem.
The cone and the front dish may, as is known, have quite considerable dimensions. They are manufactured in known manner in machines from a supply of glass by means of pressing, spinning or blowing. These known production methods require very expensive devices as well as voluminous devices used in glass technology, and this is particularly true for the manufacture of the valve cone.